Signaling system



Nav. -3l 1925.

' A. SCHMIDT, JR

SIGNALING SYSTEM l Filed July 5, 1923 //S Attorney Patented Nov. 3, 1925.

UNITI-:D STAT-Es AUGUST SCHMIDT, JR., OF SCHENECTADY,

NEW YORK, AS'SIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF YORK.

SIGNALING SYSTEM.

Application led July 3,

To all @clic-nz it may concern.'

Be it known that l, AUGE-'sr Soifririn'r, Jr.,

` a citizen ot the United States, residing at Schenectady, county oit Schenectady, State of New York, have invented certain new and useful Improvements in Signaling Systems, of which the following is a specification.

My present invention relates to `signal transmitting systems, and more particularly to systems in which an electron vdischarge device is employed for the production ot high frequency oscillations,

The object of my invention is to provide a simple and e'liicient system for controlling the amplitude of the high t'requency oscilla` tions in accordance with desired signals.

The novel features which I believe to be characteristic of my invention arel set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation will best be understood by reference to the tollowing description taken in connection with the accompanying drawing in which l have shown diagrammatically one way whereby my invention may be carried into eitect.

l have indicated in the drawing an elec tron discharge device 1 of the usual three electrode type which is connected to produce o cillations and supply them to the antenna f2 by means of the coupling transformer The oscillating circuit of device comprises an inductance l and parallel capacity 5 connected between the grid 6 and plate 7 ot the device 1. Current for the operation ot device 1 is supplied to the plate circuit from a direct current source 8, the posit-ive terminal of which is connected to the plate 7 through a high frequency choke 9 and the negative terminal of which is connected to the cathode 10 through the plate circuit of a. second three-electrode electron discharge device 11. The oscillating system of the device 1 also includes a connection from the cathode 10 to an intermediate point 12 in the inductance 4. Stopping condensers 13 prevent the flow of direct current in the oscillating circuit.

The cathode 1() of device 1 and the cathode 14 of device 11 are heated by means of alternating current su plied by transformers 15 and 16. The e` ect of the alternating current employed for heating the cathodes in varying the amplitude of the oscillations 1923. Serial N'o. 649,371.

produced is eliminated by bringing the connections from the plates and grids to the cathodes to points 17 and 18 intermediate the terminals ot the transformer secondaries in the well known manner. The same effeet is secured in the case ot' the oscillating circuit ot device 1 by making the connection from point 12 to a. point 19, which is intermediate the two condensers 20, which are connected in series across the terminals of cathode 10.

The grid circuit of device 11 includes a condenser 21 in shunt to which is connected a source ot potential 22 and a key 23. `The grid of device 1 is connected to the negative terminal ot source 8 through a high `trequency choke 9A and a resistance 25 and therebygiven a normal negative bias of the value desired l'or the eilicient production of oscillations. l

lt will be noted that current supplied to the plate circuit of device 1 has to pass through device 11. When key 23 isclosed the grid ot device 11 is made positive by source 22 so that the resistance of device 11 becomes comparatively low and device 1 de livers oscillations with 'full power to an Atenna 2. lVhen key 23 is opened the grid oit' device 11 becomes negatively charged by reason of grid condenser 21 and the resist ance. of device 11 in the plate circuit of device 1 is thereby enormously increased. The current delivered to the oscillator will be greatly decreased and at the same time the grid of device 1 will becomeso strongly negative by "reasonoit its connection to the negative terminal ot source 8 that the production ot oscillations will be entirely interrupted or their amplitude reduced to a very small percentage of their maximum ampli-V tude.

When key 23 is again closed the grid of device 11 becomes positive again permitting maximum current to be supplied to the oscillater and the grid of device 1 also becomes much less negative permitting the production of oscillations of maximum amplitude. Itl will be observed that while very high voltages may be employed in the system described, the control is effected entirely in a circuit of very low voltage and small' power and there are no moving parts required which carry large currents. The actions described also occur practically instantaneously so that it is possible to transmit signals at high speed by substituting `a moving tape control for the key 23 if desired.

Vhile I have shown and described the preferred embodiment of my invention it will be apparent that my invention is not limited to the particular embodiment shown but that many modifications in the circuit arrangements and instrumentalities employed in carrying out my invention may be made without departing from the scope thereof as set forth in the appended claims.

IVhat Ifclaim as new and desire to secure byLetters Patent of the United States, is

l. The combination in a high frequency signaling system of an electron discharge device, circuit connections for said device whereby it is adapted to produce high frequency oscillations, a second electron discharge device connected in circuit with said firstdevice in such a way that current is supplied to the first device through the second device, and means for varying the resistance of the second device substantially instantaneously from av low value to a much greater value, and simultaneously producing a large increase in the resistance of the first device.

2. The combination in a high frequency signaling system of an electron discharge device having a cathode, an anode and a controlling grid, circuit connections for said device whereby it is adapted to produce high frequency oscillations, a second similar electron discharge device connected in circuit with said first device in such a way that current is supplied to the first ,device through the second device, and means for varying the resistance of the second device substantially instantaneously from a low value to a much greater'value and simultaneously increasing the negative potential upon the grid of the first device.

3. The combination in a, high frequency signaling system of an electron discharge devicehaving a cathode, an anode and a controlling grid, a second similar electron discharge device connected in circuit with said first device in such a way that current is supplied to the first device through the second device and means for varying the potential of the grid of the second device substantially instantaneously `from a negative value sufficient to substantially interrupt the flow of current therethrough to a positive value high enough to permit maximum current to flow therethrough and simultaneously increasing the negative potential upon the grid of the first device.

4l. The combination in a high frequency signaling system of an electron discharge device having a cathode, an anode and a controlling grid, circuit connections for said device whereby it is adapted to produce high frequency oscillations, a source of direct current having its positive terminal connected to the anode of said device vand its negative terminal connected to the cathode of a second similar device, a connection from the anode of the second device to the cathode of the first device, a connection from the grid of the iii-st device to the negative terminal ofv said source, and means for substantially instantaneously varying the potential of the grid 'of the second device from a negative yvalue sufficient tosubstantially interrupt the flow of current therethrough to a positive value high enough to permit maximum current to iiow therethrough.

5. The method of operating an electron discharge device having an electron emitting cathode, an anode 'and a controlling grid with circuit connections ,connected thereto for the production of high frequency oscillations which consists in supplying current thereto through a resistance device, varying the value of the resistance of said device between a low and a comparatively high value, and simultaneously producing a high negative potential on the grid of the electron discharge device.

In witness whereof, I have hereunto set my hand this second day of July, 1923.

AUGUST SCHMIDT, J R. 

